1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, and more particularly to an electrophotographic photosensitive member containing in its photosensitive layer a specific oxytitanium phthalocyanine and a non-metallic phthalocyanine.
2. Related Background Art
In recent years, as printers for terminal equipment, non-impact type printers that apply electrophotography have replaced conventional impact type printers and have been coming into wide use. These are mainly laser beam printers using laser beams as a light source. In many instances, semiconductor lasers are used as the light source from the viewpoint of cost and apparatus size.
At present, semiconductor lasers mainly used have an oscillation wavelength which is relatively as long as 790.+-.20 nm. Accordingly, electrophotographic photosensitive members having sufficient sensitivities to such a long wavelength are being developed.
The sensitivities vary depending mainly on the types of charge-generating materials, and studies are being made on a number of charge-generating materials.
Typical charge-generating materials include phthalocyanine pigments, azo pigments, cyanine dyes, azulene dyes and squarium dyes.
Of these, as charge-generating materials having good sensitivities to long-wavelength light, researchers are recently made on metallic phthalocyanines such as aluminum chlorophthalocyanine, chloroindium phthalocyanine, oxyvanadium phthalocyanine, chlorogallium phthalocyanine, magnesium phthalocyanine and oxytitanium phthalocyanine, or non-metallic phthalocyanines.
For many phthalocyanine compounds among these, a number of crystal forms are known to exist. For example, the non-metallic phthalocyanines include an .alpha.-type, a .beta.-type, a .gamma.-type, a .delta.-type, an .epsilon.-type, a .chi.-type, and a .tau.-type. Copper phthalocyanines include an .alpha.-type, a .beta.-type, a .gamma.-type, a .delta.-type, an .eta.-type and a .chi.-type.
It is also commonly known that the crystal form has a great influence on both (1) the electrophotographic performance such as sensitivity and potential stability at the time of running and (2) the properties of coating compositions in the event the compounds are formed into coating compositions.
With regard to oxytitanium phthalocyanine also, there are many crystal forms like other phthalocyanines such as the non-metallic phthalocyanines and copper phthalocyanine as described above. For example, Japanese Patent Applications Laid-open No. 59-49544 (U.S. Pat. No. 4,444,861), No. 59-166959, No. 61-239248 (U.S. Pat. No. 4,728,592), No. 62-67094, (U.S. Pat. No. 4,664,997), No. 63-366, No. 63-116158, No. 63-198067, No. 64-17066, etc. disclose oxytitanium phthalocyanines with different crystal forms.
The oxytitanium phthalocyanines are materials having superior electrophotographic performance, but it is sought to further improve dispersion stability, sensitivity and image quality.